Louvered microwave reflector

ABSTRACT

An electromagnetic radiation beam reflector which can be made transparent or reflective by rotating its elements. The reflector is used as a secondary reflector at a microwave receiving station to compensate for signal fading due to the refraction of the electromagnetic radiation beam which causes the beam to miss the primary reflector.

United States Patent lnventor Theodore Parker Elwood, lnd.

App]. No. 887,448

Filed Dec. 22, 1969 Patented Oct, 5, 1971 Assignee Marathon Oil CompanyFindlay, Ohio LOUVERED MICROWAVE REFLECTOR 4 Claims, 4 Drawing Figs.

US. Cl 343/761, 343/781, 343/837 Int. Cl H0lq 3/12 Field of Search343/761 [56] References Cited UNITED STATES PATENTS 2,452,349 10/1948Becker 343/761 2,754,513 7/1956 Goubau.... 343/839 2,977,464 3/1961Engberg 343/912 Primary ExaminerEli Lieberman Att0rneys.loseph C.Herring, Richard C. Willson, Jr. and

Jack L. Hummel ABSTRACT: An electromagnetic radiation beam reflectorwhich can be made transparent or reflective by rotating its elements.The reflector is used as a secondary reflector at a microwave receivingstation to compensate for signal fading due to the refraction of theelectromagnetic radiation beam which causes the beam to miss the primaryreflector.

LOUVERED MICROWAVE REFLECTOR BACKGROUND OF THE INVENTION This inventionis related to the field of electromagnetic signal transmission andreception, and more specifically to the area of reflection of anelectromagnetic radiation beam.

During certain periods of the year, usually in the spring and fall,temperature inversions and other atmospheric conditions cause fading ofmicrowave signals. This fading condition is occasionally the result ofthe bending or refraction of the microwave beam. When the beam has beendisplaced enough to miss the primary reflector at the receiving station,the signal is lost and the transmission system experiences aninterruption.

A conventional corrective measure taken to restore the signal is tomount a parabolic dish receiving antenna about 40 feet below the primarystationary reflector. The parabolic dish antenna is connected to asecond receiver by a pressurized waveguide. When the signal reflectedfrom the primary stationary reflector and received by the primaryreceiver becomes weak due to atmospheric refraction of theelectromagnetic radiation beam, the secondreceiver system is utilized.This method of compensating for signal fade due to atmosphericrefraction is costly due to the capital required for equipment.

SUMMARY OF THE INVENTION The present invention comprises a variableelectromagnetic radiation beam reflector. The reflector may be mountedon an electromagnetic radiation beam receiving tower between thestationary reflector and the receiving antenna. The reflective surfacesof the variable reflector may be rotated such that an electromagneticradiation beam may pass from the stationary reflector through thevariable reflector to the receiving antenna or the reflective surfacesmay be rotated such that an electromagnetic radiation beam is reflectedfrom the variable reflector to the receiving antenna.

The advantage of the present invention is that a second receivingantenna and a second receiver are not required during the periodswhenatmospheric refraction of electromagnetic radiation beams occurs. Theinvention may be utilized in an electromagnetic beam transmission systemto avoid interruption due to atmospheric refraction of theelectromagnetic beam.

The disadvantage of using a second receiving antenna and a secondreceiver during the periods when atmospheric refraction occurs isovercome by the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The invention may be more fullyunderstood by reference to the accompanying drawings, in which:

FIG. I shows a single-element variable electromagnetic radiation beamreflector;

FIG. 2 shows a multiple-element variable electromagnetic radiation beamreflector;

FIGS. 30 and 3b show a system designed to use a variable electromagneticradiation beam reflector.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reflector of FIG. Icomprises a reflective surface 1, an

axis of rotation 2, a suitable means of support for the surface at theaxis 3, and a suitable means for causing rotation of the surface such asan actuating means comprising an actuator 4 and the connecting means 5.

The device of FIG. 2 comprises a plurality of reflectors of the typeshown in FIG. I mounted such that the axes lie in one plane and areparallel with respect to each other with a suitable means 4 and 5 forcausing each individual reflector to rotate so that the reflectorsremain parallel to each other at all positions of rotation. Thereflectors are mounted in relation to each other such that they form acommon surface when they are positioned in the same plane as the axes.

FIG. 3 is a system comprising a tower 6, a stationary electromagneticradiation beam reflector 7 mounted near the top of the tower, anelectromagnetic radiation receiving antenna 8 mounted near the bottom ofthe tower, and a variable electromagnetic radiation beam reflector 9mounted between the stationary reflector 7 and the receiving antenna 8.

The function of the:devices shown in FIG. I and FIG. 2 may be bestillustrated by their use in the system shown in FIGS. 30 and 3b. FIG. 3ashows a normal incoming electromagnetic radiation beam I0 which isreflected by reflector 7 through or past the variable electromagneticradiation beam reflector 9 to receiving antenna 8. The reflectivesurfaces of reflector 9 arerotated to a position parallel with the beampassing between stationary reflector 7 and antenna 8.

When the incoming electromagnetic radiation beam is refracted ordisplaced such that the beam strikes the tower 6 below stationaryreflector 7 as illustrated by electromagnetic radiation beam 11, thereflective surfaces of variable reflector 9 are rotated to a positionsuch that beam I1 is reflected to antenna 8.

Although two embodiments of the variable electromagnetic radiationreflector and one system utilizing the unique advantages of the variablereflector have been illustrated, it will be understood that oneexperienced in the art of electromagnetic radiation beam transmissionmay be able to make various modifications or to derive other uses.Examples of other uses, which are not intended to limit the scope of theinvention, are: the use of the variable reflector to allow the directionof one electromagnetic radiation beam to more than one target asillustrated by FIG. 3 if a transmitting antenna-or electromagneticradiation beam source were substituted for the receiving antenna 8; useof the system shown in FIG. Jfor the reception of an electromagneticradiation beam transmitted from more than one source as illustrated bysubstituting a beam from another source for the refracted beam 1 I. inFIG. 3.

What is claimed is:

I. A system which allows normal operation of an electromagneticradiation beam receiving station and compensates for the effect ofrefraction of an electromagnetic radiation beam by the atmosphere whensaid beam is caused to miss the primary reflector by said refraction,said system comprising in combination:

a. an electromagneticradiation receiving antenna mounted near theground,

b. a stationary electromagnetic radiation beam reflector mountedabove-the electromagnetic radiation receiving antenna in such a mannerso as to reflect a normal incoming electromagnetic radiation beam tosaid receiving antenna,

a multiple-element variable electromagnetic radiation beam reflectorcomprising, in combination, more than one reflective surface, eachsurface being rotatable about an axis, the axes lying in a common planeand being parallel with relationship to each other, with a means ofrotating the surfaces about said axes such that the surfaces aremaintained substantially parallel at all positions of rotation, and asupport means for supporting the rotatable surfaces, said supportsupporting the rotatable surfaces within the electromagnetic radiationbeam passing between the receiving antenna and the stationaryelectromagnetic radiation beam reflector such that the surfaces may bealternately rotated about said axes to a first position parallel to thebeam passing between the stationary reflector and the receiving antennaso as to allow the beam to pass substantially unaffected, and a secondposition such that a refracted incoming electromagnetic radiation beamwhich is caused to strike below the-stationary reflector may bereflected to the receiving anten- 2. A system which allows normaloperation of an electromagnetic radiation beam receiving station andcompensates for the effect of refraction of an electromagnetic radiationbeam by the atmosphere when said beam is caused to miss the primaryreflector by said refraction, said system comprising in combination:

a. an electromagnetic radiation receiving antenna mounted near theground,

b. a stationary electromagnetic radiation beam reflector mounted abovethe electromagnetic radiation receiving antenna in such a manner so asto reflect a normal incoming electromagnetic radiation beam to saidreceiving antenna,

c. a variable electromagnetic radiation beam reflector comprising, incombination, at least one reflective surface, such surface beingrotatable about an axis, and a support means for supporting the surfaceat the axis such that said axis is within or adjacent to theelectromagnetic radiation beam passing between the stationary reflectorand the receiving antenna such that the surface may be alternatelyrotated about said axis to a first position parallel to the beam so asto allow the beam to pass substantially unaffected and a second positionsuch that a refracted incoming electromagnetic radiation beam which iscaused to strike below the stationary reflector is reflected to thereceiving antenna.

3. The system of claim 1 wherein the multiple-element variableelectromagnetic radiation reflector mounted above the receiving antennais used to reflect the normal incoming electromagnetic radiation beam tothe receiving antenna and the stationary reflector mounted above themultiple-element electromagnetic radiation reflector is used to reflecta refracted incoming electromagnetic radiation beam, which has beencaused to strike above the variable reflector, through themultiple-element reflector to the receiving antenna.

4. The system of claim 2 wherein the variable electromagnetic radiationbeam reflector mounted above the receiving antenna is used to reflectthe normal incoming electromagnetic radiation beam to the receivingantenna and the stationary reflector mounted above the variableelectromagnetic radiation beam reflector is used to reflect a refractedincoming electromagnetic radiation beam, which has been caused to strikeabove the variable reflector, through the variable reflector to thereceiving antenna.

1. A system which allows normal operation of an electromagneticradiation beam receiving station and compensates for the effect ofrefraction of an electromagnetic radiation beam by the atmosphere whensaid beam is caused to miss the primary reflector by said refraction,said system comprising in combination: a. an electromagnetic radiationreceiving antenna mounted near the ground, b. a stationaryelectromagnetic radiation beam reflector mounted above theelectromagnetic radiation receiving antenna in such a manner so as toreflect a normal incoming electromagnetic radiation beam to saidreceiving antenna, c. a multiple-element variable electromagneticradiation beam reflector comprising, in combination, more than onereflective surface, each surface being rotatable about an axis, the axeslying in a common plane and being parallel with relationship to eachother, with a means of rotating the surfaces about said axes such thatthe surfaces are maintained substantially parallel at all positions ofrotation, and a support means for supporting the rotatable surfaces,said support supporting the rotatable surfaces within theelectromagnetic radiation beam passing between the receiving antenna andthe stationary electromagnetic radiation beam reflector such that thesurfaces may be alternately rotated about said axes to a first positionparallel to the beam passing between the statioNary reflector and thereceiving antenna so as to allow the beam to pass substantiallyunaffected, and a second position such that a refracted incomingelectromagnetic radiation beam which is caused to strike below thestationary reflector may be reflected to the receiving antenna.
 2. Asystem which allows normal operation of an electromagnetic radiationbeam receiving station and compensates for the effect of refraction ofan electromagnetic radiation beam by the atmosphere when said beam iscaused to miss the primary reflector by said refraction, said systemcomprising in combination: a. an electromagnetic radiation receivingantenna mounted near the ground, b. a stationary electromagneticradiation beam reflector mounted above the electromagnetic radiationreceiving antenna in such a manner so as to reflect a normal incomingelectromagnetic radiation beam to said receiving antenna, c. a variableelectromagnetic radiation beam reflector comprising, in combination, atleast one reflective surface, such surface being rotatable about anaxis, and a support means for supporting the surface at the axis suchthat said axis is within or adjacent to the electromagnetic radiationbeam passing between the stationary reflector and the receiving antennasuch that the surface may be alternately rotated about said axis to afirst position parallel to the beam so as to allow the beam to passsubstantially unaffected and a second position such that a refractedincoming electromagnetic radiation beam which is caused to strike belowthe stationary reflector is reflected to the receiving antenna.
 3. Thesystem of claim 1 wherein the multiple-element variable electromagneticradiation reflector mounted above the receiving antenna is used toreflect the normal incoming electromagnetic radiation beam to thereceiving antenna and the stationary reflector mounted above themultiple-element electromagnetic radiation reflector is used to reflecta refracted incoming electromagnetic radiation beam, which has beencaused to strike above the variable reflector, through themultiple-element reflector to the receiving antenna.
 4. The system ofclaim 2 wherein the variable electromagnetic radiation beam reflectormounted above the receiving antenna is used to reflect the normalincoming electromagnetic radiation beam to the receiving antenna and thestationary reflector mounted above the variable electromagneticradiation beam reflector is used to reflect a refracted incomingelectromagnetic radiation beam, which has been caused to strike abovethe variable reflector, through the variable reflector to the receivingantenna.